Semiconductor die singulation methods

ABSTRACT

Methods of singulating semiconductor die. Specific implementations may include: providing a semiconductor wafer including a plurality of die located on a first side of the semiconductor wafer where the plurality of die include a desired thickness. The method may include etching a plurality of trenches into the semiconductor wafer from the first side of the semiconductor wafer where the plurality of trenches is located adjacent to a perimeter of the plurality of die. A depth of the plurality of trenches may be greater than the desired thickness of the plurality of die. The method may also include mounting the first side of the semiconductor wafer to a tape, thinning a second side of the semiconductor wafer, exposing the plurality of trenches while thinning the second side, and singulating the plurality of die through exposing the plurality of trenches.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of the earlier U.S. UtilityPatent Application to Michael J. Seddon entitled “SemiconductorSingulation Methods,” application Ser. No. 15/189611, filed Jun. 22,2016, now pending, the disclosure of which is hereby incorporatedentirely herein by reference.

BACKGROUND 1. Technical Field

Aspects of this document relate generally to methods for singulatingsemiconductor die.

2. Background

Semiconductor die (chips) contain electronic circuits and are typicallyfabricated simultaneously on a silicon wafer. After processing of thewafer, the die need to be separated from each other so they can beeither sent for additional semiconductor packaging processing, or forinclusion into an electronic device. Some singulating techniques involveusing a saw blade. Sawing is often done in two steps, a first widerwidth saw blade cut followed by a second narrower width saw blade cutthat fully cuts through the wafer thickness.

SUMMARY

Implementations of a first method of singulating a plurality of die mayinclude: providing a semiconductor wafer including a plurality of dielocated on a first side of the semiconductor wafer where the pluralityof die include a desired thickness. The method may include etching aplurality of trenches into the semiconductor wafer from the first sideof the semiconductor wafer where the plurality of trenches is locatedadjacent to a perimeter of the plurality of die. A depth of theplurality of trenches may be greater than the desired thickness of theplurality of die. The method may also include mounting the first side ofthe semiconductor wafer to a tape, thinning a second side of thesemiconductor wafer, exposing the plurality of trenches while thinningthe second side, and singulating the plurality of die through exposingthe plurality of trenches.

Implementations of a first method of singulating a plurality of die mayinclude one, all, or any of the following:

The method may further include picking the plurality of die from thetape.

The method may further include flipping the plurality of die to transferthem from the tape to a picking tape.

Etching the plurality of trenches may further include defining a patternof the plurality of trenches using passivation material, metal material,photolithographic masking, temporary film, shadow masking, or anycombination thereof.

The semiconductor wafer may include silicon and etching the plurality oftrenches may further include using a Bosch deep reactive ion etch (DRIE)process.

The method may further include doing one of the following after etchingthe plurality of trenches: forming a plurality of bumps on the pluralityof die; testing one or more of the plurality of die; probing one or moreof the plurality of die; adding memory data to one or more of theplurality of die; forming a solderable surface on a surface of one ormore of the plurality of die, or any combination thereof.

Implementations of a second method of singulating a plurality of die mayinclude providing a semiconductor wafer including a plurality of dielocated on a first side of the semiconductor wafer where the pluralityof die include a desired thickness. The method may also include etchinga plurality of trenches into the semiconductor wafer from the first sideof the semiconductor wafer where the plurality of trenches is locatedadjacent a perimeter of the plurality of die and a depth of theplurality of trenches is greater than the desired thickness of theplurality of die. The method may further include mounting the first sideof the semiconductor wafer to a back grinding tape, thinning a secondside of the semiconductor wafer to a predetermined distance between thesecond side of the semiconductor wafer and the depth of the plurality oftrenches, and demounting the first side of the semiconductor wafer fromthe back grinding tape. The method may also include mounting the firstside of the semiconductor wafer to a picking tape and one of etching orgrinding the second side of the semiconductor wafer to expose theplurality of trenches. The method may include singulating the pluralityof die through exposing the plurality of trenches.

Implementations of the second method of singulating the plurality of diemay include one, all, or any of the following:

Etching the plurality of trenches may further include defining a patternof the plurality of trenches using passivation material, metal material,photolithographic masking, temporary film, shadow masking, or anycombination thereof.

The semiconductor wafer may include silicon and etching the plurality oftrenches may further include using a Bosch DRIE process.

The method may further include doing one of the following after etchingthe plurality of trenches: forming a plurality of bumps on the pluralityof die, testing one or more of the plurality of die, probing one or moreof the plurality of die, adding memory data to one or more of theplurality of die, forming a solderable surface on a surface of one ormore of the plurality of die, or any combination thereof.

Etching the second side of the semiconductor wafer to expose theplurality of trenches may further include etching using plasma etching,wet etching, or any combination thereof.

Thinning the second side of the semiconductor wafer to the predetermineddistance may further include using a Taiko grinding process.

Implementations of a third method of singulating a plurality of die mayinclude providing a semiconductor wafer including a plurality of dielocated one a first side of the semiconductor wafer where the pluralityof die including a desired thickness. The method may further includeetching a plurality of trenches into the semiconductor wafer from thefirst side of the semiconductor wafer where the plurality of trenches islocated adjacent a perimeter of the plurality of die and where a depthof the plurality of trenches is greater than the desired thickness ofthe plurality of die. The method may also include mounting the firstside of the semiconductor wafer to a back grinding tape, mounting thesecond side of the semiconductor wafer to a picking tape, and from thefirst side of the semiconductor wafer, etching through the predetermineddistance between the second side of the semiconductor wafer and thedepth of the plurality of trenches to singulate the plurality of die.

Implementations of the third method of singulating a plurality of diemay include one, all, or any of the following:

Etching the plurality of trenches may further include defining a patternof the plurality of trenches using passivation material, metal material,photolithographic masking, temporary film, shadow masking, or anycombination thereof.

Etching the plurality of trenches further includes defining a pattern ofthe plurality of trenches using passivation material, metal material,photolithographic masking, temporary film, shadow masking or anycombination thereof.

The semiconductor wafer may include silicon and etching the plurality oftrenches and etching through the predetermined distance both may furtherinclude using a Bosch DRIE process.

The method may further include doing one of the following after etchingthe plurality of trenches: forming a plurality of bumps on the pluralityof die, testing one or more of the plurality of die, probing one or moreof the plurality of die, adding memory data to one or more of theplurality of die, forming a solderable surface on a surface of one ormore of the plurality of die, or any combination thereof.

Thinning a second side of the semiconductor wafer to the predetermineddistance may further include using a Taiko grinding process.

Implementations of a fourth method of singulating a plurality of die mayinclude providing a semiconductor wafer including a plurality of dielocated on a first side of the semiconductor wafer, the plurality of dieincluding a desired thickness and an under bump metal layer. The methodmay include etching a plurality of trenches in to the semiconductorwafer from the first side of the semiconductor wafer where the pluralityof trenches is located adjacent a perimeter of the plurality of die anda depth of the plurality of trenches are greater than the desiredthickness of the plurality of die. The method may also include formingone or more bumps on the under bump metal layer of one or more of theplurality of die and mounting the first side of the semiconductor waferto a back grinding tape. The method may also include thinning a secondside of the semiconductor wafer to a predetermined distance between thesecond side of the semiconductor wafer and the depth of the plurality oftrenches. The method may include demounting the first side of thesemiconductor wafer from the back grinding tape, mounting the first sideof the semiconductor wafer to a picking tape, etching or grinding thesecond side of the semiconductor wafer to expose the plurality oftrenches, and singulating the plurality of die through exposing theplurality of trenches.

Implementations of a fourth method of singulating a plurality of die mayinclude one, all or any of the following:

Etching the second side of the semiconductor wafer to expose theplurality of trenches may further include etching using plasma etching,wet etching, or any combination thereof.

Thinning the second side of the semiconductor wafer to the predetermineddistance may further include using a Taiko grinding process.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a cross section view of an implementation of a wafer with aplurality of die with a patterning material/layer thereon;

FIG. 2 is a cross section view of the wafer of FIG. 1 following etchingof trenches around a perimeter of the plurality of die;

FIG. 3 is a cross sectional view of the wafer of FIG. 1 followingadditional processing steps;

FIG. 4 is a cross sectional view of the wafer of FIG. 1 flipped over andmounted to a tape;

FIG. 5 is a cross sectional view of the wafer of FIG. 1 followingthinning of a second side of the wafer, exposing the bottoms of theplurality of trenches, and singulation of the plurality of die;

FIG. 6 is a cross sectional view of the plurality of die of FIG. 5flipped over and mounted on a picking tape attached to a frame;

FIG. 7 is a cross sectional view of another implementation of a waferwith a plurality of die with a patterning material thereon;

FIG. 8 is a cross sectional view of the wafer of FIG. 7 followingetching of trenches around the perimeter of the plurality of die;

FIG. 9 is a cross sectional view of the wafer of FIG. 7 followingadditional processing steps

FIG. 10 is a cross sectional view of the wafer of FIG. 7 flipped overand mounted to a back grinding tape;

FIG. 11 is a cross sectional view of the wafer of FIG. 7 followingthinning of the second side of the wafer using a Taiko back grindingprocess;

FIG. 12 is a cross sectional view of the wafer of FIG. 7 followingdemounting of the wafer from the back grinding tape and mounting to apicking tape attached to a frame;

FIG. 13 is a cross sectional view of the wafer of FIG. 7 followingetching or grinding of the second side of the wafer, exposing thebottoms of the plurality of trenches, and singulating the plurality ofdie;

FIG. 14 is a cross sectional view of the plurality of die of FIG. 13flipped onto another picking/transporting tape;

FIG. 15 is a cross sectional view of another implementation of a waferwith a plurality of die with a patterning material thereon;

FIG. 16 is a cross sectional view of the wafer of FIG. 15 followingetching of trenches around the perimeter of the plurality of die;

FIG. 17 is a cross sectional view of the wafer of FIG. 15 followingadditional processing steps;

FIG. 18 is a cross sectional view of the wafer of FIG. 15 flipped overand mounted to a back grinding tape;

FIG. 19 is a cross sectional view of the wafer of FIG. 15 followingthinning of the second side of the wafer using a Taiko back grindingprocess;

FIG. 20 is a cross sectional view of the wafer of FIG. 15 followingdemounting of the wafer from the back grinding tape and mounting to apicking tape attached to a frame;

FIG. 21 is a cross sectional view of the wafer of FIG. 15 followingremoval of the Taiko ring;

FIG. 22 is a cross sectional view of the wafer of FIG. 15 followingetching of the wafer at the plurality of trenches to singulate theplurality of die;

FIG. 23 is a cross sectional view of a wafer having a plurality of diewhere each die includes an under bump metal layer;

FIG. 24 is a cross sectional view of the wafer of FIG. 23 followingetching of trenches around the perimeter of the plurality of die;

FIG. 25 is a cross sectional view of the wafer of FIG. 23 followingformation of a plurality of bumps on the under bump metal layer of thevarious die of the plurality of die;

FIG. 26 is a cross sectional view of the wafer of FIG. 23 followingmounting of the wafer to a back grinding tape;

FIG. 27 is a cross sectional view of the wafer of FIG. 23 followingthinning of the second side (back side) of the wafer using a Taikogrinding process;

FIG. 28 is a cross sectional view of the wafer of FIG. 23 followingdemounting of the wafer from the back grinding tape and mounting of thefirst side of the semiconductor wafer to a picking tape;

FIG. 29 is a cross sectional view of the wafer of FIG. 23 followingetching or grinding in the second side of the semiconductor wafer toexpose the bottoms of the plurality of trenches thereby singulating theplurality of die;

FIG. 30 is a cross sectional view of the wafer of FIG. 23 flipped ontoanother picking/transporting tape.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to thespecific components, assembly procedures or method elements disclosedherein. Many additional components, assembly procedures and/or methodelements known in the art consistent with the intended method forsingulating a plurality of die will become apparent for use withparticular implementations from this disclosure. Accordingly, forexample, although particular implementations are disclosed, suchimplementations and implementing components may comprise any shape,size, style, type, model, version, measurement, concentration, material,quantity, method element, step, and/or the like as is known in the artfor such methods of singulating a plurality of die, and implementingcomponents and methods, consistent with the intended operation andmethods.

During fabrication of chip scale semiconductor device packages (CSP),challenges have existed that are created as the package approaches thesize of the die, including those created by elimination of the moldcompound that covers the die and the use of bumped die. Some packagingtechnologies with more surface area can compensate for some defects inthe die, such as chipouts or cracking of the die caused during the wafersawing process (whether single pass or double pass processes). Thesawing process can also create damage along the sidewalls of the diewhich creates cracks or stress concentration points which can laterpropagate through the die and cause failures in the field. Thereliability issues created in CSP packages due to chipouts or diecracking increase as the thickness of the die themselves decreases. Manydie used in CSP processes are thinned to about 250 microns to about 500microns in thickness from the full wafer thickness. While alternativeapproaches to singulation of thinned die such as laser singulation havebeen proposed, they have not produced die with equivalent strength tosawn die due to reformation of the molten silicon side walls of the dieinto a non-single crystal structure following singulation. Because thechipouts are often on the back side of the die, they cannot beeffectively visually inspected for, so prevention of the chipoutsentirely would eliminate failures relating to these defects.

Various method implementations for singulating semiconductor die usingin whole or in part plasma etching are disclosed in this document. Thesevarious method implementations may be effective on many different wafertypes, including single crystal silicon, amorphous silicon, sapphire,silicon-on-insulator, gallium arsenide (GaAs), ruby, and any othersemiconductor substrate type, provided the plasma etch chemistry isappropriate for the specific substrate type. Furthermore, the methodimplementations may be employed with any closed shaped substrate of anysize, provided the plasma etching can be accomplished.

Where the semiconductor die include bumps (tin-silver, copper, lead-tin,etc.), attempting to use plasma etching to singulate the die on the sidewhere the bumps are present may cause processing issues resulting fromoxidation of the bump surfaces or interactions with residual materialson the bumps during the etch process, depending on the chemistry of theparticular etch involved. Accordingly, processes that do not requirethat the bumps are present during the plasma etch process may be moredesirable in some implementations to those where the bumps are in placealready.

Referring to FIG. 1, an implementation of a wafer 2 with a plurality ofdie 4 is illustrated. While in FIG. 1, the plurality of die 4 areillustrated as being the same size and the same type of die, in variousimplementations, die of different sizes and types on the same wafercould be processed in various method implementations. Each die 4 isshown has having a particular thickness 6 into the material of the wafer2. However, those of ordinary skill in the art will appreciate that thisis merely for the purposes of illustrating the desired die thickness inFIG. 1, since the process of forming the die generally means thestructure of the die is formed close to the surface of the wafer and ontop of the surface of the wafer. Accordingly, each die 4 generally canbe thinned to various thicknesses without encroaching on the activeportions of the die 4 that extend into the die. Because of this, thethickness of the die is generally determined by the packagingrequirements and packaging processing conditions.

Above each die is a layer that defines a perimeter of each die. Thislayer may be formed of any of a wide variety of etch-resistant materialssuch as, by non-limiting example, passivation material, metal material(such as under bump metallization), photoresist, temporarily appliedfilm, and any other method of patterning/providing an etch-resistantpattern on the wafer. In various implementations, shadow masking couldbe used to define the perimeter of each die. In such implementationswhere shadow masking is employed, no additional layer above each die maybe needed. Once the perimeters of the die are defined/protected by thelayer 5 (or shadow mask), a plasma etch process is used to etch aplurality of trenches 8 into the semiconductor wafer from the die side(first side) of the wafer. FIG. 2 illustrates the wafer 2 of FIG. 1following the etching process, showing that the depth/bottom 10 of theplurality of trenches lies below the desired thickness of the pluralityof die 4. Because in various method implementations, the plasma etchdoes not need to etch all the way through the full-thickness wafer, themethods may be more manufacturable and less capital intensive. As can beobserved, the plurality of trenches lie adjacent to or at the perimeterof the die.

In particular implementations, the semiconductor wafer 2 is a siliconwafer and the plasma etching process is the Bosch deep reactive ion etch(DRIE) deposition/etching process that employs, by non-limiting example,an argon/sulfur hexafluoride chemistry for etching steps andtrifluoromethane/argon chemistry for the alternating side walldeposition steps. In other implementations, however, other etchingprocesses/chemistries could be used, depending upon the particularmaterial that forms the wafer 2.

Following the etching step, the wafer may be rinsed or otherwise cleanedto remove any remaining etchant or residue from the etching process. Invarious implementations, the wafer can then have a wide variety ofadditional processes performed to the die side of the wafer. Theseinclude, by non-limiting example, forming bumps on the die; electricallytesting the die; probing the die; adding data to memory portions of thedie erased by exposure to the plasma etch process; removal of the layer5 above the die; forming a solderable surface on one or more of the die;or any other desired process that needs to be performed to the frontside of the die. This is possible because the wafer still remains atfull thickness and can be handled by standard wafer processingequipment. In various implementations, these additional processes maynot be performed, as they may be done depending upon the nature of theparticular device being formed. FIG. 3 illustrates the wafer followingapplication of a metal interconnect layer 12 to the plurality of die 4.

The wafer is then prepared for thinning. In some implementations, thisis done by mounting the die side of the wafer to back grinding tape.Such an implementation is illustrated in FIG. 4. In particularimplementations, the back grinding tape may be stiff relative to otherback grinding tapes and may or may not be supported on a frame. In otherimplementations, a wafer carrier employing a substrate may be bonded tothe back side (non-die side or second side) of the wafer 2. In otherimplementations, a wafer film frame may be employed with the varioustapes. In some implementations, the front side of the wafer may becoated with a protective layer prior to be mounted to the tape. Thisprotective layer could be a photoresist or other removable polymer orother material.

Thinning of the wafer can be accomplished by several differenttechniques. Back grinding may be used, which may include grinding acrossthe full diameter of the wafer or grinding using the Taiko processdeveloped by Disco Hi-Tec America, Inc. of Santa Clara, Calif. The Taikoprocess leaves a ring of thick wafer material (Taiko ring) around theouter edge of the backside of the wafer and grinds the center of thewafer down to the desired die thickness. In various methodimplementations, the thickness of the ring may be about 3 mm. In otherimplementations, wet chemical etching or plasma bulk etching of thematerial of the backside (second side) of the wafer may be employedeither alone or in combination with back grinding to thin the wafer. Asis illustrated in FIG. 5, the plurality of die 4 have been singulatedthrough the wafer thinning operation as the bottoms of the plurality oftrenches 8 have been exposed at the point the thinning reached thedesired thickness for the plurality of die 4 and fully removed theexcess wafer material. The singulated plurality of die are now attachedto the back grinding tape.

In various method implementations, additional processing steps could beemployed to process the back sides of the plurality of die. Bynon-limiting example, these steps could include laser marking, stressrelief etching of the die (wet etching, gas/fuming etching, plasmaetching); washing of the die; application of die attach film,application of die bonding materials, any combination thereof, or anyother desired die backside processing technique. In someimplementations, the die may be picked directly from the back grindingtape. In other implementations, the die may be flipped by beingtransferred from the back grinding tape to a picking tape for diepicking. As illustrated in FIG. 6, this picking tape 16 may be supportedby a frame 18 and the plurality of die 4 and plurality of trenches 8 arenow facing front side up again.

Various method implementations like those illustrated in FIGS. 1-6 maybe employed using wafer thinning equipment which is capable of carryingout the wafer singulation method on a single tool that can thin thewafer to singulate the plurality of die and also place the die on a filmframe without having to use a separate mounting process tool. Forexample, the tool may thin the wafer, rinse it, and then transfer thesingulated die from the back grinding tape to picking film all while thewafer is in the same tool.

Referring to FIG. 7, another implementation of a wafer 20 that includesa plurality of die 24 each with a layer 26 covering a perimeter of thedie 24 is illustrated. This wafer 20 may be any type of substratedisclosed in this document, and the die 24 may also be any disclosedherein. FIG. 8 illustrates the wafer 20 following plasma etching wherethe plurality of trenches 28 with bottoms 32 deeper than thepredetermined thickness 30 of the plurality of die have been created. InFIG. 8, the edge of the wafer shows that it has been completely etchedaway, which may be done in some implementations. However, in FIG. 8 andsubsequent figures, the edge is not shown just for the purposes ofsimplifying illustration of the method. Any of the previously discussedadditional processes may be performed to the front side of the wafer atthis point in the process. FIG. 9 illustrates the plurality of die 24following application of a metallization layer 34 to the die.

Following etching, the wafer 20 may be rinsed and then mounted with thefront side coupled to back grinding tape 36 as illustrated in FIG. 10.In this method implementation, the wafer 20 is then thinned to the pointwhere a predetermined distance between the second (back) side of thewafer and the bottom (depth) 32 of the plurality of trenches 28 isreached (partially thinned). As illustrated in FIG. 11, the backgrinding technique used for the wafer 20 was the Taiko process and theTaiko ring 38 can be observed on the back side of the wafer. However,any of the other back grinding or etching processes previously discussedcould also be used to partially thin the wafer in various methodimplementations. In particular implementations, the predetermineddistance between the bottoms 32 of the plurality of trenches 28 and thesecond side of the wafer after the partial thinning process may bebetween about 25 microns to about 100 microns. In some implementationswhere Taiko grinding is used, the predetermined distance may be betweenabout 25 microns to about 35 microns.

Referring to FIG. 12, the wafer 20 is shown following being demountedfrom the back grind tape and mounted, first side down, to a picking tape40 supported by a frame 42. At this point, the back side of the wafer iseither etched or ground to remove the remaining material of the wafer toexpose the plurality of trenches and thereby singulate the plurality ofdie from each other. In various implementations, this may involveremoving the Taiko ring, then using plasma or wet etching to remove thesilicon. While any etching process disclosed in this document could beused at this point, generally Bosch plasma etching would not be usedhere, as it would unnecessary to remove only bulk material. FIG. 13illustrates the singulated plurality of die 24 on the picking tape 40following the singulation process. The die 24 can now be picked directlyfrom the picking tape. In some implementations, the wafer 20 may not bedemounted from the back grind tape and mounted to picking tape, so theprocess of completing the singulation may take place while the wafer 20is still mounted to the back grind tape 36. In these implementations,the plurality of die 24 may be picked directly from the back grind tape36.

Any of the subsequent processes discussed in this document used forprocessing the plurality of singulated die may be utilized in variousmethod implementations, such as laser marking, stress relief etching,washing, applying die attach film, and so forth. In someimplementations, the die 24 may be flipped from the back grinding tapeor original die picking tape to another picking or other transportingtape 44 as illustrated in FIG. 14.

This method implementation may be useful as it may be less capitalintensive, as multiple process tools can be involved since the use ofthe Taiko process permits the thinned wafer to be moved from one processtool to another. Accordingly, full in-line equipment may not benecessary for use with this method implementation.

Referring to FIG. 15, another implementation of a wafer 46 with aplurality of die 48 each including a layer 50 that defines/protects theperimeters of the plurality of die 48 is illustrated. FIG. 16illustrates the wafer 46 following plasma etching of a plurality oftrenches 52 into the wafer 46. As previously discussed, the bottoms 54of the plurality of trenches 52 are located below the desired thicknessof the die 48. The etching of the wafer 46 can take place using any ofthe methods disclosed in this document, though in particularimplementations, the Bosch process is used. Any of the front side waferprocessing options previously discussed in this document may then becarried out (bumping, testing, probing, etc.). FIG. 17 illustrates thewafer 26 after a metallization layer 56 has been applied. The wafer 46is then mounted to back grinding tape 58 front side down, as illustratedin FIG. 18.

The wafer 46 is then thinned from the back side (second side) using anyof the grinding/etching process disclosed herein until the back side 60reaches a predetermined distance between the back side 60 and the bottom54 of the plurality of trenches 52. In various implementations, Taikoback grinding may be used, though standard back grinding could also beused along with bulk plasma etching or wet chemical etching. Where Taikogrinding is used, the predetermined distance may be about 25 microns toabout 100 microns. In some implementations, a wafer carrier could becoupled with the wafer as a processing aid. At this point, in thismethod implementation, any of the previously disclosed processes fortreating the back side of the plurality of singulated die may be carriedout on the back sides of the plurality of die 48. These include, bynon-limiting example, laser marking, stress relief etching, washing,applying die attach film, and any other disclosed herein. FIG. 19illustrates a wafer 46 that has been Taiko process ground showing theTaiko ring 62.

Following partial thinning of the wafer 46, the front side of the wafer46 may be demounted from the back grinding tape and then the back side(second side) of the wafer 46 may be mounted to a picking tape 64supported by a frame 66. As illustrated in FIG. 20, this process can bedone with the Taiko ring 62 in place, though in some implementations,the Taiko ring 62 may be removed following mounting using a circular sawcut process. The particular picking tape 64 may be a UV cure tape or aUV release tape in various implementations. In some implementations, apicking tape 64 may not be used but a substrate carrier/wafer carriermay be bonded to the wafer 46 or another wafer may be bonded to thewafer 46. In some implementations, the other wafer may be one whichincludes a plurality of die to be included in the finished semiconductorpackage. In various method implementations, the wafer with the backgrinding tape will be mounted to the picking tape 64 first and then theback grinding tape is then removed. In these situations, it may beeasier for the operator or equipment to remove the back grinding tapewhile the wafer is already mounted on a frame to the picking tape.

FIG. 21 illustrates the wafer 46 following removal of the Taiko ring 62.At this point, the remaining wafer material of the predetermineddistance between the bottom 54 of the plurality of trenches 52 and theback side of the wafer 6 is etched or ground away. In particularimplementations, etching process used is the Bosch process. In otherimplementations, wet etching could be used, or the wafer 46 may beflipped or otherwise mounted to allow for additional back grinding totake place. During the etching/grinding process the bottoms 54 of theplurality of trenches 52 are extended through the wafer 46 until theplurality of trenches 52 extend completely through the wafer 46 and theplurality of die 48 are singulated. Also, where the Taiko ring is stillpresent, the etching process will singulate the Taiko ring from thewafer at the same time the plurality of trenches are exposed. FIG. 22illustrates the plurality of die 48 following the singulation processattached to the picking tape 64. Since these die 48 are already frontside up, they may not need to be flipped for die picking but are alreadyto be picked directly from the picking tape 64. However, they could betransferred to another transfer tape as previously discussed in variousmethod implementations.

This method implementation may be useful in situations where capitalequipment is not available that would allow for wafer flipping and wherethe devices in the die can withstand the effects of the additionalplasma wafer processing from the front side of the wafer.

Referring to FIG. 23, another implementation of a wafer 68 isillustrated. In this implementation, the wafer 68 includes a pluralityof die 70 each of which includes a layer of under bump metal (UBM, bumpmetal layer) 72 along with associated passivation layer material whichdefines the perimeter of the die 70. The passivation layer material maybe an organic material such as, by non-limiting example, a polyimide, abenzo-cyclo-butene (BCB) material, a resin material, silicon dioxide,silicon nitride, or any other material capable of protecting the area ofthe die around the UBM. The UBM 72 in combination with the passivationlayer material serves as an etching mask during the following plasmaetching process, which may be any disclosed in this document. FIG. 24illustrates the wafer 68 following plasma etching showing the formedplurality of trenches 74, each with a bottom 76 that is below thedesired thickness of the die as previously described. In variousimplementations, one or more bumps 78 are formed on the UBM 72 throughany of a wide variety of process including, by non-limiting example,ball dropping, solder stenciling, electroplating, electroless plating,and any other process capable of forming bumps or stud bumps. Afterformation of the bumps 78, any of the front side processes disclosed inthis document may be employed, such as testing, probing, adding memory,etc. In some implementations, however, one or more of the front sideprocesses may be carried out before the bumps 78 are formed on the UBM72.

The wafer 68 is then mounted to a back grinding tape 80, bump side down,as illustrated in FIG. 26. The wafer 68 can then be thinned until theback side 82 reaches a predetermined distance between the back side 82and the bottom 76 of the plurality of trenches 74. Any of thegrinding/etching processes disclosed in this document may be used forthe partial thinning process. In various implementations, thepredetermined distance is about 25 microns to about 100 microns. Inimplementations where Taiko grinding is used, the predetermined distancemay be about 25 microns to about 35 microns. FIG. 27 illustrates thewafer following the thinning operation where the thinning has been doneusing Taiko grinding. In various implementations, the wafer 68 is thendemounted from the back grinding tape 80 and mounted to picking tape 84supported by a frame 86 with the front side of the wafer 68 down, asillustrated in FIG. 28. In various implementations, the picking tape 84may be UV cure or UV release tape. In other implementations, however,picking tape 84 may not be used and the wafer 68 may be bonded to asubstrate carrier or other wafer as previously described.

In some implementations where Taiko grinding was used, the Taiko ring isthen removed using any of the processes disclosed in this document. Atthis point, the remaining material of the wafer 68 is etched using anyprocess disclosed in this document until the bottoms 76 of the pluralityof trenches 74 are exposed, thereby singulating the plurality of die 70,as illustrated in FIG. 29. Since the die 70 are supported by the pickingtape 84, they may be directly picked from the tape, or any of thepreviously disclosed operations may be used to additionally process theback sides of the die, such as, by non-limiting example, laser marking,stress relief etching, washing, adding die attach film, and so forth. Insome implementations, the die 70 will be flipped onto another picking ortransport tape for die picking or transporting. In some implementations,the die will be placed into another carrier, such as a waffle pack forsubsequent processing. FIG. 30 illustrates the plurality of die 70flipped onto another die picking tape, now with the bump side of the dieup.

In various method implementations, the UBM 72 may be formed and in placebefore the trenches are etched. However, in other implementations, thetrenches could be formed first and the UBM then formed on the die. Thismay be accomplished, by non-limiting example, by using an electrolessplating process, such as a nickel/gold process to form the UBM. Becauseelectroless plating does not require an electrical connection to theback side of the plurality of die, the metal can still be deposited evenwhen the die are electrically isolated through the plurality oftrenches.

In places where the description above refers to particularimplementations of methods of singulating die and implementingcomponents, sub-components, methods and sub-methods, it should bereadily apparent that a number of modifications may be made withoutdeparting from the spirit thereof and that these implementations,implementing components, sub-components, methods and sub-methods may beapplied to other methods of singulating die.

What is claimed is:
 1. A method of singulating a plurality of die, themethod comprising: providing a semiconductor wafer comprising aplurality of die located on a first side of the semiconductor wafer, theplurality of die comprising a desired thickness; etching a plurality oftrenches into the semiconductor wafer from the first side of thesemiconductor wafer, the plurality of trenches located adjacent aperimeter of the plurality of die and a depth of the plurality oftrenches being greater than the desired thickness of the plurality ofdie; mounting the first side of the semiconductor wafer to a backgrinding tape; thinning a second side of the semiconductor wafer to apredetermined distance between the second side of the semiconductorwafer and the depth of the plurality of trenches; from the first side ofthe semiconductor wafer, etching through the predetermined distancebetween the second side of the semiconductor wafer and the depth of theplurality of trenches to singulate the plurality of die.
 2. The methodof claim 1, wherein etching the plurality of trenches comprises plasmaetching.
 3. The method of claim 1, wherein etching the plurality oftrenches further comprises defining a pattern of the plurality oftrenches using one of passivation material, metal material,photolithographic masking, temporary film, shadow masking, and anycombination thereof.
 4. The method of claim 1, wherein the semiconductorwafer comprises silicon and etching the plurality of trenches andetching through the predetermined distance both further comprise using aBosch deep reactive ion etch (DRIE) process.
 5. The method of claim 1,further comprising one of the following after etching the plurality oftrenches: forming a plurality of bumps on the plurality of die; testingone or more of the plurality of die; probing one or more of theplurality of die; adding memory data to one or more of the plurality ofdie; forming a solderable surface on a surface of one or more of theplurality of die; and any combination thereof.
 6. The method of claim 1,wherein thinning the second side of the semiconductor wafer to thepredetermined distance further comprises using a Taiko grinding process.7. The method of claim 1, further comprising picking the plurality ofdie from the back grinding tape.
 8. A method of singulating a pluralityof die, the method comprising: providing a semiconductor wafercomprising a plurality of die located on a first side of thesemiconductor wafer, the plurality of die comprising a desiredthickness; etching a plurality of trenches into the semiconductor waferfrom the first side of the semiconductor wafer, the plurality oftrenches located adjacent a perimeter of the plurality of die and adepth of the plurality of trenches being greater than the desiredthickness of the plurality of die; mounting the first side of thesemiconductor wafer to a back grinding tape; thinning a second side ofthe semiconductor wafer to a predetermined distance between the secondside of the semiconductor wafer and the depth of the plurality oftrenches; demounting the first side of the semiconductor wafer from theback grinding tape; mounting the second side of the semiconductor waferto a picking tape; from the first side of the semiconductor wafer,etching through the predetermined distance between the second side ofthe semiconductor wafer and the depth of the plurality of trenches tosingulate the plurality of die.
 9. The method of claim 8, whereinetching the plurality of trenches comprises plasma etching.
 10. Themethod of claim 8, wherein etching the plurality of trenches furthercomprises defining a pattern of the plurality of trenches using one ofpassivation material, metal material, photolithographic masking,temporary film, shadow masking, and any combination thereof.
 11. Themethod of claim 8, wherein the semiconductor wafer comprises silicon andetching the plurality of trenches and etching through the predetermineddistance both further comprise using a Bosch deep reactive ion etch(DRIE) process.
 12. The method of claim 8, further comprising one of thefollowing after etching the plurality of trenches: forming a pluralityof bumps on the plurality of die; testing one or more of the pluralityof die; probing one or more of the plurality of die; adding memory datato one or more of the plurality of die; forming a solderable surface ona surface of one or more of the plurality of die; and any combinationthereof.
 13. The method of claim 8, wherein thinning the second side ofthe semiconductor wafer to the predetermined distance further comprisesusing a Taiko grinding process.
 14. A method of singulating a pluralityof die, the method comprising: providing a semiconductor wafercomprising a plurality of die located on a first side of thesemiconductor wafer, the plurality of die comprising a desiredthickness; etching a plurality of trenches into the semiconductor waferfrom the first side of the semiconductor wafer, the plurality oftrenches located adjacent a perimeter of the plurality of die and adepth of the plurality of trenches being greater than the desiredthickness of the plurality of die; mounting the first side of thesemiconductor wafer to a back grinding tape; thinning a second side ofthe semiconductor wafer to a predetermined distance between the secondside of the semiconductor wafer and the depth of the plurality oftrenches; from the first side of the semiconductor wafer, etchingthrough the predetermined distance between the second side of thesemiconductor wafer and the depth of the plurality of trenches tosingulate the plurality of die; and transferring the plurality of diefrom the back grinding tape to a transporting tape.
 15. The method ofclaim 14, wherein etching the plurality of trenches comprises plasmaetching.
 16. The method of claim 14, wherein etching the plurality oftrenches further comprises defining a pattern of the plurality oftrenches using one of passivation material, metal material,photolithographic masking, temporary film, shadow masking, and anycombination thereof.
 17. The method of claim 14, wherein thesemiconductor wafer comprises silicon and etching the plurality oftrenches and etching through the predetermined distance both furthercomprise using a Bosch deep reactive ion etch (DRIE) process.
 18. Themethod of claim 14, further comprising one of the following afteretching the plurality of trenches: forming a plurality of bumps on theplurality of die; testing one or more of the plurality of die; probingone or more of the plurality of die; adding memory data to one or moreof the plurality of die; forming a solderable surface on a surface ofone or more of the plurality of die; and any combination thereof. 19.The method of claim 14, wherein thinning the second side of thesemiconductor wafer to the predetermined distance further comprisesusing a Taiko grinding process.
 20. The method of claim 14, furthercomprising picking the plurality of die from the transporting tape.